diff --git a/src/corelib/io/qprocess.cpp b/src/corelib/io/qprocess.cpp
index f58783d510..67385e2698 100644
--- a/src/corelib/io/qprocess.cpp
+++ b/src/corelib/io/qprocess.cpp
@@ -1942,10 +1942,16 @@ QByteArray QProcess::readAllStandardOutput()
 */
 QByteArray QProcess::readAllStandardError()
 {
-    ProcessChannel tmp = readChannel();
-    setReadChannel(StandardError);
-    QByteArray data = readAll();
-    setReadChannel(tmp);
+    Q_D(QProcess);
+    QByteArray data;
+    if (d->processChannelMode == MergedChannels) {
+        qWarning("QProcess::readAllStandardError: Called with MergedChannels");
+    } else {
+        ProcessChannel tmp = readChannel();
+        setReadChannel(StandardError);
+        data = readAll();
+        setReadChannel(tmp);
+    }
     return data;
 }
 
diff --git a/tests/auto/corelib/io/qprocess/tst_qprocess.cpp b/tests/auto/corelib/io/qprocess/tst_qprocess.cpp
index 80005a7284..16b7dc666f 100644
--- a/tests/auto/corelib/io/qprocess/tst_qprocess.cpp
+++ b/tests/auto/corelib/io/qprocess/tst_qprocess.cpp
@@ -1082,6 +1082,16 @@ void tst_QProcess::mergedChannels()
 
     QVERIFY(process.waitForStarted(5000));
 
+    {
+        QCOMPARE(process.write("abc"), qlonglong(3));
+        while (process.bytesAvailable() < 6)
+            QVERIFY(process.waitForReadyRead(5000));
+        QCOMPARE(process.readAllStandardOutput(), QByteArray("aabbcc"));
+        QTest::ignoreMessage(QtWarningMsg,
+            "QProcess::readAllStandardError: Called with MergedChannels");
+        QCOMPARE(process.readAllStandardError(), QByteArray());
+    }
+
     for (int i = 0; i < 100; ++i) {
         QCOMPARE(process.write("abc"), qlonglong(3));
         while (process.bytesAvailable() < 6)